Rubber-modified styrene resins, in particular, acrylonitrile butadiene styrene (ABS) resins have excellent impact resistance, high heat resistance, high stiffness, good moldability, and the like. Hence, the ABS resins have been widely used for sundries, automotive interior and exterior components, housings and components for household electrical appliances such as electric rice cookers and microwave ovens, and housings and components for office automation (OA) equipment such as telephones and facsimiles.
In recent years, to improve weather resistance, a shortcoming, of ABS resins, acrylonitrile acrylic styrene (AAS) resins have been developed by substituting acrylic rubbers having few double bonds for butadiene rubbers having double bonds that are unstable to light and heat, in the rubber components of the ABS resins. Unfortunately, acrylic rubbers exhibit lower impact resistance than butadiene rubbers.
A method for adding an organic silicone oil to improve the impact resistance of the AAS resin or the ABS resin is disclosed in Japanese Unexamined Patent Application Publication No. 2001-31830. However, in the conventional method for adding the organic silicone oil, an addition of a large amount of the silicone oil causes a problem in which a molded product has an undesired surface.
A method for adding a polyorganosiloxane-containing graft copolymer in order to improve secondary processability of the rubber-modified styrene resin is disclosed in Japanese Unexamined Patent Application Publication No. 7-331025. However, when the polyorganosiloxane content in the polyorganosiloxane-containing graft copolymer is high, it is difficult to process the graft copolymer into a powder form. Furthermore, when the polyorganosiloxane-containing graft copolymer is added to the rubber-modified styrene resin, a problem arises in that the resulting resin has an undesired appearance and low impact resistance.